CRCoV is a highly contagious respiratory infection which is spread by direct dog-to-dog contact, aerosols of respiratory secretions, and contact with contaminated environments or people. Some dogs have a mild disease with symptoms consisting of cough, sneezing, and nasal discharge, while other dogs have a subclinical infection with no clinical signs, yet they shed virus that can infect other dogs. Dogs infected with CRCoV may progress to pneumonia, particularly if co-infected with other respiratory pathogens.
Dogs infected with multiple respiratory pathogens, particularly both viral and bacterial pathogens, may contract canine infectious respiratory disease complex (CIRDC), which is a highly contagious multifactorial disease common in dogs housed in crowded conditions, such as re-homing centers and boarding or training kennels. Respiratory pathogens seen in dogs infected with CIRD include the bacterium Bordetella bronchiseptica (Bemis et al., Lab. Anim. Sci., 29:48-52, 1977), canine respiratory coronavirus (CRCoV) (Erles et al., Virology, 310(2):216-223, 2003), canine influenza virus (CIV) (Crawford et al., Science, 310(5747):482-485, 2005), canine parainfluenzavirus (CPIV) (Binn et al., Exp. Biol. Med., 126:140-145, 1967), Mycoplasma cynos (Chalker et al., Microbiology, 150:3491-3497, 2004), and canine adenovirus serotype 2 (CAV-2) (Ditchfield et al., Can. Vet. J., 3:238-247, 1962). To date, no vaccine against all, or the majority, of the aforementioned pathogens has emerged.
Protection against CIRDC and other multi-pathogen diseases has traditionally focused on the administration of a combination vaccine that includes immunogens targeted against each of the potential pathogens.